Reversible radial air gap eddy current clutch



Jan. 12, 1954 A. s. GUTMAN REVERSIBLE RADIAL AIR GAP EDDY CURRENT CLUTCH 2 Sheets-Sheet 1 Filed May 17, 1951 IPA/O w m m7 V m6 a k9 Q m Mm Q m L Q a Y B Q Q 3 M N m* m h Mm hMv m, 3. K w 3 hw Nw/ r /Wa\r| a ms w E 4 v NM on i K WWW Lip 721M 14 6 Jan. 12, 1954 A.s. GUTMAN 2,666,154 I REVERSIBLE RADIAL AIR GAP EDDY CURRENT CLUTCH Filed May 17, 1951 ,2 Sheets-Sheet 2 IN V EN TOR. I ,qmem 5. 60mm Patented Jan. 12, 1954 STATES PATENT ortrce REvEflslBLE RADlALh-Allt- EDDi1".- CURRENT CLUTCH;

Alltried .SILG tm Brooklizie. Mass...

Application May 1'1, 1951,: Serial No'. 2.26,926-

(Cl-.fifi'rr-QQ),

(Granted under Title 35, 1 'S. Code (1952);

sec. 266) .Claims.

. 1 The invention described herein may be manu ia'ctured and used by; or for the United -State5 Government for governmental purposes; without payment to me of any; royalty thereon;

This invention relates to eddy current-clutches of- '-thisinvention to provide a relatively :small air gap between an" eddy current memberand magnetic poles w-hlch hereto-fore has -beenimpossible.-=

Attempts "have been;made -in -the 'J9;St"'t0i increase the torque :of eddy current -;clutches in speed=regulation--servosby useof magnetic fluid. Howevemthis :presents --dimeulties1-such as keep; ing the iron-particlesin --suspensien-, preventingdeteriorati'on of the "fluid due to oxidation;, and properly sealing the-fluid,- which has abrasive qualities. Further,experiencehas shown. that the ---viscous drag in a-- magneticfluidrclut'ch' is considerable and prevents 'high" speed =operation without excessive heat-3 development. Therefore; it is -a-further object ofthis invention to provide ---an eddy -currentclutch, using a radial air: gap:-and'- floating eddy current member as" semblyy so as -to "perm-it a "srnall air gap without maintaining:- unreasonable machining tolerances and-thereby develop high torque without requiring-a magnet-ic flui'de" Itz is a -sti ll further object-ofthis invention to provide an eddy current clutch servo comprising aapair f:v :rotors oppositely driven-by--an input means-coils mounted ineach of the rotors, up shamed-members positioned over saidrotors and 90115 'lSQQ-thfit the rotors and. i the cup: shaped members provide northand south poles. A pair ,2. eddrcurrent. .s1eere=.-members .arezfloatingly mounted.;-.orer-.- he month iandisouthripoles and 1 mterlockawi hua idissa The disc 5 is :connected to an outnutshatt :socth t 11mineither one ot'th lfl blfirbe ingcfinfir i fid. t-a will be createdbe nonmagnetic mitergearsl6, l6 and I5".

tweencneofthe eddyeurrent members and poles so that the eddycurrent member will rotate with that rotor and thereby rotatethe disc and output-shaftin-the direction of that rotor. In order for the output shaftto be rotatedin theopposite direction the other'rotor is energized sothat the other :sleeve will rotate with that rotor in the opposite direction thereby rotating the shaft'in the opposite direction; By :floatinglypositionin 'the-eddy--current sleeve members over-the north-and south-poles *a close radial air gap is obtained which-gives higher torque; values and also takes careofthe ;machining eccentriciti'es between the various elements. The, eddy; current sleeve members are free to float sincethey have their own separate centers of rotation.

Other objects-twill become apparent as the invention is described in detail;'referenee being had to the drawing; wherein;

Fig. 1 is an axial section taken at |'-I 'oif Figs.

2 "or *3 -th1'0tlgh'*the improved "clutch' which is the subject =of--thisinvention 2 is I a central transverse section taken at 2 -2 of Fig.1 throughthedriven element :of the :device.

Fig. 3 'is a transverse section taken .at,,3i3 of Fig; 1 throughg-thepoles of one of the two mag: netic 1 pole assemblies.

Figured is a view showing the relationship of---the poles sleeve members and output disc.

Referring-now to the drawing an aluminum (nonmagnetic) housing In is bored oniour sides as'at l2, l2, l2 and 12"". Bores l2, l2, and [2' supportball bearings 14, I4 and I", re speotively, whichin'turn support bronze or other Bore I'2"-""-is used to support a plastic terminaliplate 18;: Aluminum-cover plateslfl and 26" enclose ball beari-ngs l4 and H. Amotor "enc1oses the bore 42'." and-is drivably connected, throughthe inputshaft'zd, to-the miter gear 16".; Thecorer plates 2l},= 20'-, the terminal plate 18 andthe. mo: tor 25 are-allhe1dito the housing by screws. 23

A main'output shaft-22 made from 18 8 stainless steel-or other nonmagnetic material and the input shaft=24 aresupported for rotation in the housing to by-ball'bearings26, 26"and 26", respectively; which 'are in turn supportedin the end plates-26:20 and'the motor -25: Pi-nions 28 and 28: are-secured to the shaft 22 by-keys 3D and 30' and nuts 3| and 3|. Thrust bearings 32 and. 321': are providedto tak'e the axial thrust of the :shaft 22-.1

Attached to the irmerface of ;the miter gears lit :and fli hy=scrcvsrs-3 l and 34 are the ferromagnet core and coil assemblies 35 and 35' which comprise cylindrical coil and core portions 36 and 36 each having a flange 38 and 38' at the outer end and a circumferentially spaced series of pole lugs 46 or 40 at the inner end, the coils 42 and 42 being wound between the flanges 38 or 38' and the lugs 4|! and 40, whichever coil is being wound. Slip rings 4| and 41 are insulatedly carried on the outside of the core and coil assemblies 35 and 35'. Brushes 43 extend from terminal posts 45 through which the coils 42 and 42' may be selectively energized. The thrust bearings 32 and 32' on the output shaft 22 hold the shaft against axial movement. The iron coil cover members 44 and 44' surround the coil flanges 38 and 38 and have a series of lugs 46 and 46' extending axially toward each other.

Iron sleeves 48 and 48 surround lugs 40 and 46 toward each other from the iron sleeves 48 and .48. The disc 50 has six notches, three of which are occupied by the three rightward extending teeth 52 on sleeve 48 and three of which are occupied by the three leftward extending teeth .52 on sleeve 46.

Referring only to the left hand core and coil assembly 35, the coil 42 is wound on the magnetic core 36 between the integral flanges 38 and 40 of the core. The left flange 38 is circular and is tapped for the screws 34. The right hand flange, however, is V-notched at six places so as to be divided into the six poles 40 (see Fig. 3). The cup shaped iron cover 44 is thickened at the open end of the cup and this open end is cut away at six places so as to leave lugs 46 on the cup extending axially toward the right into the V notches between poles 40 (see Fig. 3), and leaving air gaps of considerable size between between adjacent poles 40 and 46. The input shaft 24 is always driven in the same direction whereby the miter gears I6 and I6 are rotated in the opposite direction. When current is passed through the coil 42, magnetic flux flows axially through the core 36, then radially to the outer ends of poles 40, at which point the flux in each pole 40 divides, half jumping the air gap at the right of a pole 40 and the other half jumping an air gap to the left of the pole 40. The flux now returns through the negative poles 46 on the outer ends of the cover 44, then through the cover 44, then radially inward through the flange 38 back to the beginning. It is noted that the flux for each pole travels circumferentially only at the endcs of the positive poles 40, across the air gaps between positive poles 40 and negative poles 46 and into the negative poles 46. It is at these points that the outer ends of the poles 46 and 46 lie close up to the inner surface of the sleeve 48. In order to show the several parts more clearly, however, the actual space between the outer ends of the poles 46 and 46 and the inner surface of the sleeve 48 is greatly magnified in the drawing, the actual space being only .0005 inch, whereas for clarity this space is enlarged.

It is pointed out that one floating sleeve member may be used in single direction motors wherever high torque values are desired,

I claim:

1. An eddy current clutch which comprises a hollow housing, an output shaft having rotative bearing in the ends of said hollow housing, a pair of axially spaced apart mitre gears concentrically surrounding and freely rotatable about the axis of said output shaft, an input shaft having bearing in said housing with axis normal to the axis of the output shaft, a third mitre gear on said input shaft in mesh with said pair of axially spaced mitre gears, an ironcladelectromagnetic core and coil assembly concentricallysecured at the outer end to the inner face of each of the said axially spaced mitre gears with north and south poles at the inner end facing each other, a nonmagnetic disc fast on the output shaft between the ends of the pole pieces, said disc having an even number of peripheral notches, sleeves, one on each side of said disc having a continuous surface freely surrounding said pole pieces, said sleeves each having lugs on the inner edges extending into the peripheral notches in said discs. said continuous surfaces forming eddy current members so that upon being energized the sleeve will drive said non-magnetic disc and output shaft.

2. An eddy current clutch which comprises a housing, an output shaft having rotative bearing in said housing, a peripherally notched nonmagnetic disc fast on said shaft intermediate the ends thereof, a free floating sleeve on each side of said disc, said sleeves each having a continuous, surface and a series of lugs extending axially into one or more of the peripheral notches, two cylindrical coaxial ironclad electromagnets, one adjacent each side of said disc, both rotatable freely on said output shaft and both having poles rotatable freely inside said sleeves, means to simultaneously rotate said electromagnets one opposite the other and means to selectively energize said electromagnets, said continuous surfaces forming eddy current members so that upon being energized the sleeve will drive said magnetic disc and output shaft.

3. The structure defined in claim 2 wherein, at the end adjacent the nonmagnetic disc, the core of the ironclad electromagnet has a series of pole pieces extending radially, and where the cover of the ironclad electromagnet, at the end adjacent the nonmagnetic disc, has an equal number of pole pieces extending axially between the radial pole pieces leaving airgaps therebetween, so that the flux travels circumferentially at the poles and the both ends, across the air gap therebetween and through the adjacent sleeve;

4. In an eddy current clutch comprising in combination an input means, a pair of rotors adapted to be rotated in opposite directions by said input means, poles on said rotors, an output shaft, a disc secured to said output shaft, a pair of eddy current sleeve members adapted to rotate said disc in two directions, said sleeve members being floatingly positioned about said rotor and about said poles, said sleeve members adapted to center themselves about said rotors and poles upon relative rotation therebetween Without binding and thereby permitting a small radial air gap, said sleeve members having an axis of rotation separately movable from the axis of the rotor and poles.

5. In an eddy current clutch servo, said clutch adapted to produce high torque values as a result of small radial air gaps, said clutch comprising a rotor provided with poles, an eddy current sleeve member floatingly positioned adjacentto the poles of the rotor to form a small air gap therebetween, said sleeve member having an axis of rotation which is movable with respect to the axis of rotation of the rotor and poles so as to center itself therewith, whereby unreason- 5 able manufacturing tolerances are not required Number to maintain a small radial air gap. 2,289,330 ALFRED S. GU'IMAN. 2,313,466 2,305,963 References Cited in the file of this patent 5 57 UNITED STATES PATENTS Number Name Date Number 803,322 Bacon Oct. 31, 1905 752 79 919,460 Price Apr. 27, 1909 1,756,671 Alden Apr. 29, 1930 Name Date Fischer July 7, 1942 Dieke Mar. 9, 1943 Hanson Dec. 22, 1942 Jacobs Sept. 5, 1944 FOREIGN PATENTS Country Date France July 24, 1933 

